Elevator push button switch



s. B. SANFORD ET AL 2,051,654

ELEVATOR PUSH BUTTON SWITCH Aug. 18, 1936.

Filed March 2, 1934 INVENTORS ATTORNEY Patented Aug. 18, 1936 UNITEDSTATES ELEVATOR PUSH BUTTON SWITCH Selden Bradley Sanford and David CarlLarson,

Yonkers, N. Y., assignors to Otis Elevator Company, New York, N. Y., acorporation of New Jersey Application March 2, 1934, Serial No. 713,636

1 Claim.

This invention relates to elevator push button switches. Characteristicof such switches are the push button switches, or elevator hall pushbuttons, as they are termed, provided in the halls of buildings foractuation by those desiring elevator service.

It has long been known in the elevator field that the provision of hallpush button switches which are at once easy of operation, pleasing inappearance, economical to make and to maintain, and efiective asintended under all circumstances, is a diflicult undertaking. At thefoundation of this problem is the fact that hall push buttons forelevators are subject to many forms of abuse, intentional as well asunintentional. Such abuse results either in the destruction of the pushbutton switch, or of some part thereof, or in the alteration of thenormal operation of the push button switch, with either of such resultsimpairing the elevator service and necessitating repairs or replacementsor both. The impairment of elevator service is a subtle, but vastlyimportant I consequence of abuse of elevator hall push buttons. Theabuse may result in failure of the push button switch, when actuated, toregister desire for elevator service. The consequent long wait for anelevator car to stop at that floor is destructive to building prestige.In addition, it is usually not until this condition has existed for sometime that the building management is apprised of it, and by thenappreciable dissatisfaction with the elevator service may have accrued.The abuse, on the other hand, may result in causing the push buttonswitch continuously to register desire for elevator service, regardlessof whether there is anyone at the floor actually desiring service. As aconsequence, elevator cars stopping at that floor in response to theapparent desire for service therefrom, many times find no one there. Afalse and useless stop'by the elevator car is not, at any time,complimentary of the elevator service, and since such a stop is clearlyperceived by those in the elevator car, only a few such experiencescause users of the elevators to question the reliability of the elevatorservice, with consequent reflection against the character of thebuilding. In addition, incident to every false and useless stop by anelevator car is the loss of a certain amount of time. In the aggregate;considering the number of elevator cars which make false stops at afloor where the hall push button switch is continuously registering, andthe number of false stops made at that floor by each of such cars duringthe course of even only a fraction of a day, the total loss of timeocca'- sioned by the continuously registering push button switch isenormous. This loss of time is detrimental to the elevator service, andthus, also to building prestige.

It is clear, therefore, that even if elevator 5 hall push buttonswitches in a building are rendered ineffective or abnormally effectiveonly occasionally, the situation is serious, not only in the directrepair and replacement costs involved, but also in the impairment of theelevator service and thus, in the impairment of the character andreputation of the building.

The need for elevator hall push button switches which always operateonly as intended, regardless of abuse of every character, intentionaland unintentional, is clearly apparent.

The principal abuses to which. push button switches are subject whenprovided as elevator hall buttons, are four. These are:

1. Blows or excessive pressure upon the pres sure-receiving element,either with blunt or sharp instruments, as, for example, umbrellas.These tend to fracture or otherwise injure the pressurereceiving elementand other movable parts of the push button switch.

2. Sticking of the pressure-receiving element in the in position. Thiscan be effected with the majority of push button switches by the use oftooth picks, pins, chewing gum, and similar articles.

3. Sticking of the pressure-receiving element in the out position. Thisis usually more diflicult of attainment than the preceding form ofabuse, but in certain types of push button switches can be effected bythe use of chewing gum, elastic bands, and the like. This, and thepreceding form of abuse, are very frequently experienced in officebuildings, where they are usually perpetrated by office, messenger anddelivery boys.

4. Blows or force applied in a direction transverse to the motion of thepressure-receiving element. The most common form of this type of abuseresults from the side-swiping'of the push button switch by trucks andother carriers, and is due to the fact that in many cases portions ofthe push button switches project outwardly from the wall an appreciabledistance.

The object of this invention is the provision of a push button switchwhich is tamper-proof, which always operates only as intended,regardless of all forms of abuse and attempted abuse, which is simple inconstruction and operation, which is readily and cheaply manufacturedand installed, which is pleasing in appearance, and

which, in spite of all forms of abuse, has a long, useful life.

The invention involves the provision of a small, thin, elastic, metallicdiaphragm serving as a pressure-receiving member, the diaphragm beingsupported at its periphery by a suitable mounting. Manual depression ofthe diaphragm is transmitted to a movable contact member which engagesor separates from a stationary contact member to close or open anelevator signal or control circuit. In the preferred construction, astop is provided in rear of the diaphragm, over substantially the entirearea of the pressure-receiving portion thereof, for limiting the inwardmotion of the diaphragm to a small value, with provision for causingmovement of the contact portion of the movable contact member an amountgreater than such limited motion of the diaphragm. Preferably thediaphragm is made of non-corrosive metal, such as beryllium copper,hardened after forming, with the pressure-receiving portion thereofself-returning. Preferably also the diaphragm mounting is arranged sothat the edge thereof is substantially flush with the wall on which thepush button switch is mounted.

In the drawing:

Figure 1 is a front elevation of a portion of the exterior of anelevator hall push button switch assembly in accordance with theinvention;

Figure 2 is aside elevation thereof, with certain parts shown insection;

Figure 3 is a rear elevation thereof;

Figure 4 is a detail of certain of the parts thereof; and

Figure 5 is a sectional view thereof taken along the line 5-5 of Figure2.

Referring to the drawing, the elevator hall push button switch assemblyshown therein comprises a push button unit generally designated I I, asupporting plate l2, a receptacle I3, and a cover plate I4. Forsimplicity, only the immediately adjacent portions of the supportingplate I2, the receptacle I3 and the cover plate I4 are shown. Pushbutton unit I I comprises a cylindrical plug member I5, a diaphragm I3,a contact assembly I1, and certain other parts to be described later.The push button unit is mounted in a suitable aperture in supportingplate I2 and secured therein by means of two fingers I8, one end of eachof which is fastened, as by screws 23, to plate I2, and the other end ofeach of which fits into a circumferential groove 2| formed in plugmember I5.

To receptacle I3 adjacent the top edge of sup porting plate I2 isadjustably mounted, as by screw 22, a bracket 23 having a front lip 24and two rear lips 25. The space between the plane of the front lip andthe plane of thetwo rear lips is such that, after bracket 23 is securedto receptacle I3, the top edge of supporting plate I2 may be inserted insuch space and the plate moved upwardly from the position in which it isillustrated in order that the bottom edge of the plate may be insertedbetween the lips of a similar bracket at the bottom of receptacle I3.Cover plate I4 encloses the front of receptacle I3, and is secured inplace by screws 26 (only one being illustrated) which extend throughapertures therein and through suitably threaded apertures in supportingplate I2. Cover plate I4 is provided with one or more aperturescorresponding to the number of push button units II enclosed by thecover plate, arranged so that each aperture fits over a correspondingplug member i5, with the circumferential edges of the diaphragm I5substantially flush with the front face of the cover plate. Preferablyreceptacle I3 is mounted in the supporting wall (not shown) so thatcover plate I4 is parallel thereto and substantially flush therewith.

Plug member I5 is preferably formed as a single solid metallic piece andarranged so that its front face 21 is substantially flush with the frontface of cover plate I4. Diaphragm I6 is positioned over front face 21 ofplug member I5 and is provided with a plurality of bent-over lips 39engaging the sides of a circumferential groove 3| directly behind frontface 21 to maintain the diaphragm in position. Diaphragm I 5 is made ofextremely thin, elastic, metallic material and preferably is formed sothat its pressure-receiving area. is displaced outwardly from the frontface 2'! of plug member I5, the shape for such bulgingpressure-receiving area being that of a spheroidal shell of relativelylarge radius. In addition, the elasticity and shape of the diaphragm arepreferably such that the pressurereceiving area thereof isself-returning to its initial position so long as such area is notdisplaced past the plane of the circumferential edges of the diaphragm.

An aperture 32 is provided through plug member I5 from front face 21 torear face 33, this aperture preferably being along the cylindrical axisof the plug member. Slidably fitted in aperture 32 is a push pin 34,preferably of insulating material, with the end thereof abutting againstthe inner surface of diaphragm I6. The other end of push pin 34 abutsagainst a push bar 35, preferably of insulating material and ofrectangular cross-section. A transverse slot 36 is formed in push bar35, and along the unslotted side of the push bar is positioned a keystrip 31, the key strip being secured to the push bar, as by the rivet43. The functions of push pin 34, push bar 35, slot 36 and key strip 31will appear as the description proceeds.

The contact assembly generally designated I1 is mounted on rear face 33of plug member I5. As illustrated, it comprises two leaf springs-astationary one M and a movable one 42separated by an insulating washer43 and secured to plug member I5 by two screws 44, insulating washers 45being provided at either side of the leaf springs. It is preferred toprovide also a metallic cap washer 46 and lock washers 41 adjacent theheads of screws 44, and an insulator piece 53, covering substantiallyall of rear face 33, between such face and the immediately adjacentwasher 45. Stationary leaf spring 4| is shaped to provide a terminal tab5 I. Movable leaf spring 42 may also be shaped to provide a similarterminal tab, but it is preferred to employ for this purpose a separatemetallic spacing washer 52, with terminal tab 53, interposed betweenleaf spring 42 and insulating washer 43, metallic spacing washer 52being less wide than insulating washer 43. Terminal tabs 5I and 53 maybe connected into an elevator signal or control circuit by means ofwhich intending passengers register their desire for elevator service.

Movable leaf spring 4?. is provided with an aperture 54 (see Figure 4)through which passes push bar 35 and key strip 31, with a tongue 55 ofleaf spring 42 arranged to fit into slot 35 on the push bar. As a resultof this construction, motion of push bar 35 to the right, as viewed inFigure 2, due to the application of pressure upon diaphragm l6 and theconsequent displacement of push pin 34, causes leaf spring 42 to bendabout its base so that the outer end of leaf spring 42 moves toward theouter end of leaf spring 4|. The ends of these leaf springs areprovidedwith suitable contact points 56, preferably of compositions inwhich silver or rare metals of the platinum group, such as palladium,predominate. The application of pressure upon diaphragm l6 thus resultsin the engagement of these contact points at the ends of the leafsprings, and thus in the completion of a circuit from terminal tab 5| toterminal tab 53.

At the side of aperture 54 in leaf spring 42 opposite to tongue is ashoulder 51. This shoulder, together with key strip 31 to which it isadjacent, prevents disengagement of push bar 35 from tongue 55. Inassembling these parts, push bar 35, without key strip 3'! attachedthereto, is first inserted in aperture 54 until slot 36 is oppositetongue 55. The push bar is then moved transversely in aperture 54 sothat tongue 55 fits into slot 35. Key strip 31 is then inserted inaperture 54 along the back of push bar 35 and secured in place, as bythe rivet 40. Push bar 35 and key strip 31 are preferably of suchdimensions that, when secured together, they are guided by the sides ofaperture 32 in plug member l5, as illustrated in Figure 5.

It is preferred to provide stationary leaf spring 4| with an enlargedaperture through which may extend the ends of push bar 35 and key strip31. In this connection, it is to be noted that contact assembly I! mayinclude leaf spring contacts in addition to the two illustrated, suchadditional contacts being readily mounted on plug member l5 by screws 44in the same manner as are the two contacts illustrated so that a stackof contacts results, and the movable leaf spring contact of each pair ofcontacts in such stack being actuated by push bar 35 (elongated ifnecessary) in the same manner as leaf spring contact 42 is actuated. Itis also to be noted that normally closed leaf spring contacts may asreadily be employed as the normally open leaf spring contactsillustrated, and further, that contact assembly I! may include anycombination of normally open and normally closed contacts.

Attention is directed to the fact that front face 21 of plug member l5acts as a stop for diaphragm I 6 and thus restricts to a small value theinward motion of the diaphragm, regardless of the amount of pressureapplied thereto. In addition, front face 2'! is preferably in the sameplane as the circumferential edges of the diaphragm, as illustrated, sothat the diaphragm cannot be deformed past such plane. Diaphragm l6, notbeing rigidly secured to plug member i5, is free to give a small amountat its periphery upon deformation by the application of pressurethereto. Upon the removal of the pressure causing the deformation ofdiaphragm IS, the diahragm returns of its own accord to its originalposition. Diaphragm I3 is preferably made of thin, elastic, metallicmaterial that may be hardened after formation into the desired shape,although it may be made of any thin, hard, puncture-proof, elasticmaterial. The preferred metallic material for diaphragm I6 is copperwith about 2 beryllium, heat treated, after formation, at about 525 F.for an hour and then air cooled. The resulting diaphragm is almost ashard as steel, is non-corrosive, withstands much abuse, is not readilycut or punctured, and is elastic. It has been found that a diaphragm l6of such material, with an inside diameter of 1 inches, a thickness of5/1000 inch, and arranged in a push button unit such as illustrated sothat the maximum inward motion is about inch, undergoes without failureservice equivalent to over sixty years service as a hall push button ina heavy traific building.

Attention is also directed to the fact that by the construction hereindescribed and illustrated, s

its ends, and enables, for a given amount of relative motion of thecontact points, the use of a diaphragm of smaller diameter than isotherwise possible. The importance of a small diameter diaphragm fromthe viewpoint of artistic appearance in elevator lobbies is readilyappreciated. Also of importance is a. construction in which only acomparatively small, but-discernible motion of the diaphragm is requiredto actuate the push button contacts, since constructions requiring largemotions of the diaphragm will be insufliciently actuated by the generalpublic. Multiplication of the diaphragm motion thus also results inobtaining sufficient relative motion of the contact points conjointlywith the desired small amount of diaphragm motion. In the illustratedconstruction the multiplication ratio is approximately 2 to- 1.

The movable leaf spring 42 is preferably of thin, elastic, metallicmaterial. Beryllium copper, similar to that of which the diaphragm ispreferably made, and similarly heat treated, had been found to givesatisfactory service for leaf spring 42. In order to minimize localbending in leaf spring 42, and thus to assist in attaining long life forleaf spring 42, aperture 54 is provided with special flares asillustrated, although other shapes may be employed.

It is to be noted that with the construction for the push button switchherein described, the installation thereof may be effected in stages asthe progress of the building construction .advances. Thus, receptacle l3may be mounted in the supporting wall at the time the conduit isinstalled, which is usually before any plastering takes place. At somelater date, the wiring-is drawn through the conduit and the wire endsleft free in the receptacle. At a still later date, when the buildingnears completion and the elevator installation is about to be set inoperation, the push button unit or units H for each receptacle I3 havetheir terminal tabs 5| and 53 connected to the appropriate Wire ends.Push button unit or units H are then secured to supporting plate [2 andthe supporting plate inserted between the lips of upper bracket 23 and acorresponding lower bracket (not shown). Cover plate I4 is then securedin place by screws 26, this operation also securing in place supportingplate l2. In the event replacement or repair of any part of push buttonunit II should become necessary, it is to be noted that the entire unitmay be removed with ease and a complete new unit substituted in placethereof. The interruption of the elevator service from that floor isconsequently a minimum, and, if desired, the repair or replacement ofthe injured part of the removed push button unit may be effected at alater and more convenient time.

Inasmuch as many changes could be made in the above construction andmany apparently Widely different embodiments of this invention could bemade without departing from the scope thereof, it is intended that allmatter contained in the above description or shown in the accompanyingdrawing shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

A tamper-proof elevator push button switch comprising; a cylindricalmember having a front face, a rear face, an aperture substantially alongthe axis thereof between the two faces, and a circumferential groovejust behind the front face to form a circular bead around the front endof the member, the front of said bead curving back from said front faceto the periphery of the bead and the rear of said bead sloping back fromsaid periphery into said groove; switching mechanism mounted on saidrear face of said member; a manually depressible circular diaphragm ofthin, elastic, metallic material having a body portion shaped as aportion of a spheroidal shell of relatively large radius, said diaphragmhaving lips for securing said diaphragm in position over said front facewith said body portion extending outwardly therefrom, the edge of saiddiaphragm being curved to conform with the curvature of said bead up tothe periphery of the bead and said lips extending inwardly from theperiphery of the bead and being bent to fit against the rear of saidbead, thereby securing the diaphragm to said member in such way that thediaphragm is free to give radially outwardly at its edge upon pressurebeing applied to the diaphragm, thus permitting the diaphragm to bedepressed, said front face preventing inward motion of said diaphragmpast the plane of the periphery of said body portion, and said diaphragmbeing self-returning from all resulting depressible positions; and apush rod abutting against the inside surface of said diaphragm andsliding in, and guided by, said aperture in said cylindrical member foroperating said switching mechanism.

SELDEN BRADLEY SANFORD. DAVID CARL LARSON.

